1. Field of the Invention
The invention relates to a semiconductor structure, and more particularly to a semiconductor structure tolerating higher voltages.
2. Description of the Related Art
Field Effect Transistors (FETs) comprise Metal Oxide Semiconductor FETs (MOSFETs). MOSFETs are widely applied in analog circuits or digital circuits. MOSFETs comprise N type MOSFETs and P type MOSFETs according to channel types. The N type MOSFETs are called NMOSFETs. The P type MOSFETs are called PMOSFETs. Structures of MOSFETs comprise vertical structures and lateral structures. Because lateral structures are easily integrated with the present semiconductor technology, lateral structures are more frequently utilized. The MOSFETs comprising lateral structures are called Lateral Diffused MOSFETs (LD_MOSFETs).
Generally, each LD_MOSFET comprises a drift region. The length of the drift region is increased according to conventional method such that the LD_MOSFET has the capability for tolerating higher voltages. Thus, usable space is reduced and the equivalent impedance of the LD_MOSFET is increased when the LD_MOSFET is turned on.